We propose to continue our studies attempting to identify, isolate and characterize an integral membrane protein which, as we have hypothesized, must be a ubiquitous protein that directly or indirectly provides the membrane binding site for membrane-associated actin in eukaryotic cells. We also propose to continue our studies to determine whether specific proteins, particularly cytoskeletal proteins, undergo a change in their steady state level of phosphorylation in fibroblasts transformed by wild-type and temperature-sensitive mutants of Rous sarcoma virus.